It would be handy if we could speak in different languages (except in megaphones). Makes it easier for our foreign friends... I mean people are using romanized versions anyway like annyeong instead of 안녕
I believe the current client (and any English version of MapleStory) doesn't allow for non-ASCII characters. To my knowledge (and I could be wrong), there isn't a way to fix this without using a client not based off GMS.